1. Field of the Invention
The invention relates to a communication system in which a telephone terminal performs telephone communications, via a communication control apparatus, with a destination telephone terminal accommodated in an external network, and more particularly to a communication system that allows a telephone call to be initiated from an information terminal accommodated in the communication system.
2. Description of the Related Art
When initiating a call from a telephone terminal connected to a public telephone network (hereinafter called an ordinary telephone terminal), the caller has to enter the telephone number of the destination telephone terminal by operating numeric keys or the dial on the telephone. The caller manually enters the telephone number by looking it up in a paper-based telephone directory or by searching through telephone numbers managed by a telephone directory application program incorporated in a portable personal information terminal such as a PDA (Personal Digital Assistant) terminal. On the other hand, with the commercial implementation of VoIP (Voice over Internet Protocol) technology that performs transmission and reception of voice data in IP packet form using a TCP/IP (Transmission Control Protocol/Internet Protocol) network, telephone terminals specifically designed for VoIP (hereinafter simply called VoIP telephone terminals) have come to be used for telephone communications. In this case also, the caller manually enters telephone numbers in the same manner as with an ordinary telephone. To manually enter a telephone number, the caller first takes the telephone off-hook thus sending an off-hook signal and, after receiving a dial tone from the exchange, enters the destination telephone number by operating numeric keys, etc. thereby sending selection signals corresponding to the entered telephone number (hereinafter, transmission of an off-hook signal, reception of a dial tone, and transmission of selection signals are collectively called the initiation of a call).
One way to initiate a call from a VoIP telephone terminal may be by using a telephone directory application program stored in the telephone; however, because of the need for smaller size and increased functionality of the telephone, the display screen of the telephone is often made small and, with many letters and numbers displayed on the limited screen area, the caller may erroneously recognize the destination telephone number when searching telephone numbers by using the telephone directory application program. Furthermore, with the small keypad of the telephone, the user may press wrong keys when manually entering the telephone number. Erroneous recognition of the telephone number or entering of wrong keys results in making a call to the wrong party.
The VoIP telephone terminal, which uses a TCP/IP network as earlier described, is often connected to a personal computer or the like in a manner that enables communication between them, and in view of this, techniques for initiating a call using a personal computer have been proposed in order to prevent wrong number dialing.
For example, according to the description given in Japanese Unexamined Patent Publication JP-A 10-336304 (1998), a personal computer detects the off-hook condition of a telephone terminal connected to it, and activates the telephone application program or telephone directory application program stored in the personal computer. This saves the user the trouble of locating the program and activating it.
According to the description given in Japanese Unexamined Patent Publication JP-A 11-41294 (1999), when the user specifies a telephone number in home page data displayed on a client terminal such as a personal computer, a WWW (World Wide Web) server on which the home page data is stored transmits necessary data, including the selected telephone number and the Internet telephone software name associated with that telephone number, to the client terminal. The client terminal that received the data activates the Internet telephone software designated by the Internet telephone software name, and establishes a voice communication link with the destination telephone terminal. In this way, while browsing the home page, the user can perform voice communications with a telephone terminal connected to the ordinary telephone network.
According to Japanese Unexamined Patent Publication JP-A 2001-127902 (2001), when the user operates the VoIP telephone terminal, an information terminal such as a personal computer automatically activates a telephone directory application program and displays the telephone directory data on the screen. When the user selects the destination telephone number from the telephone directory data, the selected telephone number is transmitted from the information terminal to the VoIP telephone terminal which then automatically initiates a call to the received telephone number. This makes it possible to initiate a call without the user having to manually enter the telephone number, and serves to enhance the ease of operation of the telephone terminal.
In the prior art described above, when initiating a call from the VoIP telephone terminal, telephone directory data has to be downloaded from an external server or data such as the destination telephone number has to be transferred from a personal computer to the VoIP telephone terminal, and this has lead to the problem that the operation is cumbersome and it takes time before the call can be actually initiated.